This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Small molecules form the basis of communication, defense, and behavior in many organisms. We have elucidated several of the chemical cues in the nematode Caenorhabditis elegans that control behavior, including dauer formation and mating. These signaling molecules add to the wealth of biological data already established for C. elegans, providing the key components to learning more about nematode ecology and behavior. Nematodes are the most abundant animals on earth, occupy virtually every ecological niche, and thus provide an outstanding opportunity for comparative studies of animal behavior. This information is important to human health, because billions of people and large numbers of crops in the world are infected with parasitic nematodes.Our current studies focus on two groups of small molecules, the ascarosides and a family of steroidal bile acids, which serve important functions in behavior and development of nematodes. Central to the proposed research is the use of new NMR-spectroscopic methodology (DANS) that permits the analysis of complex small molecule mixtures and greatly accelerates both the structure elucidation process and the functional characterization of the detected compounds.